Disposing of waste material by incineration in a rotating kiln, or retort, is well known in the art. In most incinerators, however, the flame is applied directly to the waste material whereby, the flame combustion gases and the gases from the waste material intermingle. Because of the hazardous nature, that mixture cannot be released into the atmosphere unless the hazardous components are removed in exhaust stack gas cleaning and scrubbing apparatus and special permits are obtained. The installation of those cleaning and scrubbing apparatus and the issuance of those permits are time consuming and very uneconomical.
In other applications, rotating kilns are placed in an oven that is sealed from the inside chamber of the kiln and the drum is exposed directly to the flame. These configurations have several disadvantages. One disadvantage is that the direct flame weakens the drum. Another disadvantage is that the drum may develop hot spots thereby, causing the waste material to stick to the interior drum walls. Another disadvantage is that such ovens normally have a high exhaust gas temperature and are, therefore, very inefficient.
U.S. Pat. No. 3,020,212, teaches how to reclaim usable materials from refuse by having a flame outside of the retort chamber. That patent, however, does not disclose recirculating the hot exhaust gases, using a rotating drum, recovering the condensable vapors or exchanging heat between the effluent vapors and the feed.
U.S. Pat. No. 3,787,292, discloses retorting a waste material in a chamber separated from the combustion gases. That patent, however, does not disclose the recirculation of hot exhaust gases, but the exposure of the drum walls to direct flame. U.S. Pat. No. 4,439,209, also teaches how to retort a waste material in a separate rotating drum inside an oven without recirculating the exhaust gases.
It is, therefore, an object of the present invention to provide an apparatus for efficiently retorting a waste material into its separate phases of liquid, solids, and gases, without commingling the separate phases of the waste material with the atmosphere or with the heater combustion gases.
It is also an object of the present invention to provide an apparatus for efficiently retorting a waste material by providing a first inside chamber for the waste material, a second outside chamber for providing a flow of hot gases to impart heat to the inside chamber, an additional chamber for containing a burner zone, and means for pumping hot gases from one end of the second chamber around the burner zone for cooling the fire tube and blending with the products of combustion and back to the other end of the second chamber.
It is also an object of the present invention to teach how to prevent the waste materials from sticking to the inside wall of the rotating drum by providing a special scraper.
It is also an object of the present invention to teach how to control the flow of solids through the rotating drum by providing internal baffles with retaining walls.
It is also an object of the present invention to provide a more efficient retort by recirculating the hot exhaust gases back through the burner zone.
It is also an object of the present invention to provide a more efficient retort by cross exchanging heat from the hot solid waste material to the combustion air.
It is also an object of the present invention to provide a more efficient retort by cross exchanging heat from the vapors from the waste materials to the feed.
It is also an object of the present invention to provide an apparatus for retorting a material and means for separating the heavier liquids from the lighter liquids from said retorted material.
It is also an object of the present invention to provide an apparatus for retorting a material and means for separating the heavier oils from the lighter oils from said retorted materials.
Other objects and advantages of the invention will become more apparent upon a consideration of the preferred embodiments described hereinafter.